// Helper function for the normalize() mixin.
@function _normalize-include($section, $exclude: null) {
    // Initialize the global variables needed by this function.
    @if not global_variable_exists(_normalize-include) {
      $_normalize-include: () !global;
      $_normalize-exclude: () !global;
    }
    // Since we are given 2 parameters, set the global variables.
    @if $exclude != null {
      $include: $section;
      // Sass doesn't have static variables, so the work-around is to stuff these
      // values into global variables so we can access them in future calls.
      $_normalize-include: if(type-of($include) == 'list', $include, ($include)) !global;
      $_normalize-exclude: if(type-of($exclude) == 'list', $exclude, ($exclude)) !global;
      @return true;
    }
  
    // Check if $section is in the $include list.
    @if index($_normalize-include, $section) {
      @return true;
    }
    // If $include is set to (all), make sure $section is not in $exclude.
    @else if not index($_normalize-exclude, $section) and index($_normalize-include, all) {
      @return true;
    }
    @return false;
  }
  
  @mixin normalize($include: (all), $exclude: ()) {
    // Initialize the helper function by passing it this mixin's parameters.
    $init: _normalize-include($include, $exclude);
  
    // If we've customized any font variables, we'll need extra properties.
    @if $base-line-height != 24px
      or $base-unit != 'em'
      or $h2-font-size != 1.5  * $base-font-size
      or $h3-font-size != 1.17 * $base-font-size
      or $h4-font-size != 1    * $base-font-size
      or $h5-font-size != 0.83 * $base-font-size
      or $h6-font-size != 0.67 * $base-font-size {
      $normalize-vertical-rhythm: true !global;
    }
  
    /*! normalize-scss | MIT/GPLv2 License | bit.ly/normalize-scss */
  
    @if _normalize-include(document) {
      /* Document
         ========================================================================== */
  
      /**
       * 1. Correct the line height in all browsers.
       * 2. Prevent adjustments of font size after orientation changes in
       *    IE on Windows Phone and in iOS.
       */
  
      html {
        @if $base-font-family {
          /* Change the default font family in all browsers (opinionated). */
          font-family: $base-font-family;
        }
        @if $base-font-size != 16px or $normalize-vertical-rhythm {
          // Correct old browser bug that prevented accessible resizing of text
          // when root font-size is set with px or em.
          font-size: ($base-font-size / 16px) * 100%;
        }
        @if $normalize-vertical-rhythm {
          line-height: ($base-line-height / $base-font-size) * 1em; /* 1 */
        }
        @else {
          line-height: 1.15; /* 1 */
        }
        -ms-text-size-adjust: 100%; /* 2 */
        -webkit-text-size-adjust: 100%; /* 2 */
      }
    }
  
    @if _normalize-include(sections) {
      /* Sections
         ========================================================================== */
  
      /**
       * Remove the margin in all browsers (opinionated).
       */
  
      body {
        margin: 0;
      }
  
      /**
       * Add the correct display in IE 9-.
       */
  
      article,
      aside,
      footer,
      header,
      nav,
      section {
        display: block;
      }
  
      /**
       * Correct the font size and margin on `h1` elements within `section` and
       * `article` contexts in Chrome, Firefox, and Safari.
       */
  
      h1 {
        @include normalize-font-size($h1-font-size);
        @if $normalize-vertical-rhythm {
          @include normalize-line-height($h1-font-size);
        }
  
        @if $normalize-vertical-rhythm {
          /* Set 1 unit of vertical rhythm on the top and bottom margins. */
          @include normalize-margin(1 0, $h1-font-size);
        }
        @else {
          margin: 0.67em 0;
        }
      }
  
      @if $normalize-vertical-rhythm {
        h2 {
          @include normalize-font-size($h2-font-size);
          @include normalize-line-height($h2-font-size);
          @include normalize-margin(1 0, $h2-font-size);
        }
  
        h3 {
          @include normalize-font-size($h3-font-size);
          @include normalize-line-height($h3-font-size);
          @include normalize-margin(1 0, $h3-font-size);
        }
  
        h4 {
          @include normalize-font-size($h4-font-size);
          @include normalize-line-height($h4-font-size);
          @include normalize-margin(1 0, $h4-font-size);
        }
  
        h5 {
          @include normalize-font-size($h5-font-size);
          @include normalize-line-height($h5-font-size);
          @include normalize-margin(1 0, $h5-font-size);
        }
  
        h6 {
          @include normalize-font-size($h6-font-size);
          @include normalize-line-height($h6-font-size);
          @include normalize-margin(1 0, $h6-font-size);
        }
      }
    }
  
    @if _normalize-include(grouping) {
      /* Grouping content
         ========================================================================== */
  
      @if $normalize-vertical-rhythm {
        /**
         * Set 1 unit of vertical rhythm on the top and bottom margin.
         */
  
        blockquote {
          @include normalize-margin(1 $indent-amount);
        }
  
        dl,
        ol,
        ul {
          @include normalize-margin(1 0);
        }
  
        /**
         * Turn off margins on nested lists.
         */
  
        ol,
        ul {
          ol,
          ul {
            margin: 0;
          }
        }
  
        dd {
          margin: 0 0 0 $indent-amount;
        }
  
        ol,
        ul {
          padding: 0 0 0 $indent-amount;
        }
      }
  
      /**
       * Add the correct display in IE 9-.
       */
  
      figcaption,
      figure {
        display: block;
      }
  
      /**
       * Add the correct margin in IE 8.
       */
  
      figure {
        @if $normalize-vertical-rhythm {
          @include normalize-margin(1 $indent-amount);
        }
        @else {
          margin: 1em $indent-amount;
        }
      }
  
      /**
       * 1. Add the correct box sizing in Firefox.
       * 2. Show the overflow in Edge and IE.
       */
  
      hr {
        box-sizing: content-box; /* 1 */
        height: 0; /* 1 */
        overflow: visible; /* 2 */
      }
  
      /**
       * Add the correct display in IE.
       */
  
      main {
        display: block;
      }
  
      @if $normalize-vertical-rhythm {
        /**
         * Set 1 unit of vertical rhythm on the top and bottom margin.
         */
  
        p,
        pre {
          @include normalize-margin(1 0);
        }
      }
  
      /**
       * 1. Correct the inheritance and scaling of font size in all browsers.
       * 2. Correct the odd `em` font sizing in all browsers.
       */
  
      pre {
        font-family: monospace, monospace; /* 1 */
        font-size: 1em; /* 2 */
      }
    }
  
    @if _normalize-include(links) {
      /* Links
         ========================================================================== */
  
      /**
       * 1. Remove the gray background on active links in IE 10.
       * 2. Remove gaps in links underline in iOS 8+ and Safari 8+.
       */
  
      a {
        background-color: transparent; /* 1 */
        -webkit-text-decoration-skip: objects; /* 2 */
      }
    }
  
    @if _normalize-include(text) {
      /* Text-level semantics
         ========================================================================== */
  
      /**
       * 1. Remove the bottom border in Chrome 57- and Firefox 39-.
       * 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
       */
  
      abbr[title] {
        border-bottom: none; /* 1 */
        text-decoration: underline; /* 2 */
        text-decoration: underline dotted; /* 2 */
      }
  
      /**
       * Prevent the duplicate application of `bolder` by the next rule in Safari 6.
       */
  
      b,
      strong {
        font-weight: inherit;
      }
  
      /**
       * Add the correct font weight in Chrome, Edge, and Safari.
       */
  
      b,
      strong {
        font-weight: bolder;
      }
  
      /**
       * 1. Correct the inheritance and scaling of font size in all browsers.
       * 2. Correct the odd `em` font sizing in all browsers.
       */
  
      code,
      kbd,
      samp {
        font-family: monospace, monospace; /* 1 */
        font-size: 1em; /* 2 */
      }
  
      /**
       * Add the correct font style in Android 4.3-.
       */
  
      dfn {
        font-style: italic;
      }
  
      /**
       * Add the correct background and color in IE 9-.
       */
  
      mark {
        background-color: #ff0;
        color: #000;
      }
  
      /**
       * Add the correct font size in all browsers.
       */
  
      small {
        font-size: 80%;
      }
  
      /**
       * Prevent `sub` and `sup` elements from affecting the line height in
       * all browsers.
       */
  
      sub,
      sup {
        font-size: 75%;
        line-height: 0;
        position: relative;
        vertical-align: baseline;
      }
  
      sub {
        bottom: -0.25em;
      }
  
      sup {
        top: -0.5em;
      }
    }
  
    @if _normalize-include(embedded) {
      /* Embedded content
         ========================================================================== */
  
      /**
       * Add the correct display in IE 9-.
       */
  
      audio,
      video {
        display: inline-block;
      }
  
      /**
       * Add the correct display in iOS 4-7.
       */
  
      audio:not([controls]) {
        display: none;
        height: 0;
      }
  
      /**
       * Remove the border on images inside links in IE 10-.
       */
  
      img {
        border-style: none;
      }
  
      /**
       * Hide the overflow in IE.
       */
  
      svg:not(:root) {
        overflow: hidden;
      }
    }
  
    @if _normalize-include(forms) {
      /* Forms
         ========================================================================== */
  
      /**
       * 1. Change the font styles in all browsers (opinionated).
       * 2. Remove the margin in Firefox and Safari.
       */
  
      button,
      input,
      optgroup,
      select,
      textarea {
        font-family: if($base-font-family, $base-font-family, sans-serif); /* 1 */
        font-size: 100%; /* 1 */
        @if $normalize-vertical-rhythm {
          line-height: ($base-line-height / $base-font-size) * 1em; /* 1 */
        }
        @else {
          line-height: 1.15; /* 1 */
        }
        margin: 0; /* 2 */
      }
  
      /**
       * Show the overflow in IE.
       */
  
      button {
        overflow: visible;
      }
  
      /**
       * Remove the inheritance of text transform in Edge, Firefox, and IE.
       * 1. Remove the inheritance of text transform in Firefox.
       */
  
      button,
      select { /* 1 */
        text-transform: none;
      }
  
      /**
       * 1. Prevent a WebKit bug where (2) destroys native `audio` and `video`
       *    controls in Android 4.
       * 2. Correct the inability to style clickable types in iOS and Safari.
       */
  
      button,
      html [type="button"], /* 1 */
      [type="reset"],
      [type="submit"] {
        -webkit-appearance: button; /* 2 */
      }
  
      button,
      [type="button"],
      [type="reset"],
      [type="submit"] {
  
        /**
         * Remove the inner border and padding in Firefox.
         */
  
        &::-moz-focus-inner {
          border-style: none;
          padding: 0;
        }
  
        /**
         * Restore the focus styles unset by the previous rule.
         */
  
        &:-moz-focusring {
          outline: 1px dotted ButtonText;
        }
      }
  
      /**
       * Show the overflow in Edge.
       */
  
      input {
        overflow: visible;
      }
  
      /**
       * 1. Add the correct box sizing in IE 10-.
       * 2. Remove the padding in IE 10-.
       */
  
      [type="checkbox"],
      [type="radio"] {
        box-sizing: border-box; /* 1 */
        padding: 0; /* 2 */
      }
  
      /**
       * Correct the cursor style of increment and decrement buttons in Chrome.
       */
  
      [type="number"]::-webkit-inner-spin-button,
      [type="number"]::-webkit-outer-spin-button {
        height: auto;
      }
  
      /**
       * 1. Correct the odd appearance in Chrome and Safari.
       * 2. Correct the outline style in Safari.
       */
  
      [type="search"] {
        -webkit-appearance: textfield; /* 1 */
        outline-offset: -2px; /* 2 */
  
        /**
         * Remove the inner padding and cancel buttons in Chrome and Safari on macOS.
         */
  
        &::-webkit-search-cancel-button,
        &::-webkit-search-decoration {
          -webkit-appearance: none;
        }
      }
  
      /**
       * 1. Correct the inability to style clickable types in iOS and Safari.
       * 2. Change font properties to `inherit` in Safari.
       */
  
      ::-webkit-file-upload-button {
        -webkit-appearance: button; /* 1 */
        font: inherit; /* 2 */
      }
  
      /**
       * Correct the padding in Firefox.
       */
  
      fieldset {
        padding: 0.35em 0.75em 0.625em;
      }
  
      /**
       * 1. Correct the text wrapping in Edge and IE.
       * 2. Correct the color inheritance from `fieldset` elements in IE.
       * 3. Remove the padding so developers are not caught out when they zero out
       *    `fieldset` elements in all browsers.
       */
  
      legend {
        box-sizing: border-box; /* 1 */
        display: table; /* 1 */
        max-width: 100%; /* 1 */
        padding: 0; /* 3 */
        color: inherit; /* 2 */
        white-space: normal; /* 1 */
      }
  
      /**
       * 1. Add the correct display in IE 9-.
       * 2. Add the correct vertical alignment in Chrome, Firefox, and Opera.
       */
  
      progress {
        display: inline-block; /* 1 */
        vertical-align: baseline; /* 2 */
      }
  
      /**
       * Remove the default vertical scrollbar in IE.
       */
  
      textarea {
        overflow: auto;
      }
    }
  
    @if _normalize-include(interactive) {
      /* Interactive
         ========================================================================== */
  
      /*
       * Add the correct display in Edge, IE, and Firefox.
       */
  
      details {
        display: block;
      }
  
      /*
       * Add the correct display in all browsers.
       */
  
      summary {
        display: list-item;
      }
  
      /*
       * Add the correct display in IE 9-.
       */
  
      menu {
        display: block;
  
        @if $normalize-vertical-rhythm {
          /*
           * 1. Set 1 unit of vertical rhythm on the top and bottom margin.
           * 2. Set consistent space for the list style image.
           */
  
          @include normalize-margin(1 0); /* 1 */
          padding: 0 0 0 $indent-amount; /* 2 */
  
          /**
           * Turn off margins on nested lists.
           */
  
          menu &,
          ol &,
          ul & {
            margin: 0;
          }
        }
      }
    }
  
    @if _normalize-include(scripting) {
      /* Scripting
         ========================================================================== */
  
      /**
       * Add the correct display in IE 9-.
       */
  
      canvas {
        display: inline-block;
      }
  
      /**
       * Add the correct display in IE.
       */
  
      template {
        display: none;
      }
    }
  
    @if _normalize-include(hidden) {
      /* Hidden
         ========================================================================== */
  
      /**
       * Add the correct display in IE 10-.
       */
  
      [hidden] {
        display: none;
      }
    }
  }
